Behavior of electron-nuclear systems (molecules) is analyzed in terms of the theory of quantum measurements. It is shown that the nuclear subsystem takes the part of analyzer of a measuring device with respect to quantum coherent states (superpositions - linear combinations of resonating structures) of electronic subsystem. Using this result the problem of electronic structure of π-system of benzene molecule is readdressed. It is shown that the latter may be represented as a superposition of observable structures in variance with usual widely spread assumption of their fundamental inaccessibility for observation. On this base more general view of chemical experiment as of special case of general measurement procedure performed on quantum system is substantiated and some of its consequences are presented. In the frame of the same approach a comparison between behavior of electron-nuclear systems and action of quantum computers (processors) and presence of a deep analogy between them is demonstrated.